Ethers for aromatizing purposes

ABSTRACT

The invention relates to novel ethers and their use as aroma precursors. The ethers are derived from ionol and related compounds. These aroma precursors do not have a substantial aroma as such under ambient conditions, but will break up into a complex mixture having useful organoleptic properties under heating. The ethers are especially suitable for use in products which are heated, burned or smouldered in some stage of their use. The compounds according to the invention are especially suitable for application to tobacco. Mixtures obtained by degrading (e.g. by heating) the ethers according to the invention may be used in a flavouring or perfuming mixture as well due to their organoleptic properties.

The present invention relates to ethers and to their use as aromaprecursors. More specifically the invention relates to ethers derivedfrom ionol or related compounds and to their decomposition into aromacompounds on heating. Additionally, the invention relates to a processfor preparing said ethers.

In the art of flavouring it is known to use so called precursorcompounds which themselves do not have the desired organolepticproperties, but which under the conditions of use of the flavouredproducts decompose, thus giving a desired flavour compound. Simpleesters such as acetates of flavouring alcohols have been used for thispurpose.

However, there is a constant need for new aroma precursors whichthemselves are relatively non-volatile, which are reasonablythermostable and only break up into volatile aromatizing compounds onsubstantial heating or under pyrolysing conditions.

Also there is a need for aroma precursors which, on decomposition,provide a well-balanced mixture of aroma notes rather than merely asingle aromatizing compound.

It has now been found that ethers derived from ionol or relatedcompounds exhibit no substantial aroma as such, but on heating break upinto complex aromatizing mixtures or compositions of volatile compounds.

The ethers according to the invention have the formula R₁ --O--R₂, withR₁ and R₂ being radicals according to the following structural formula:##STR1## wherein R denotes either hydrogen or a lower alkyl group.Preferably R is hydrogen or methyl. Double bonds may be present at thepositions indicated by the dotted lines. Preferably at least one doublebond is present in the radicals R₁ and R₂. Furthermore, R₁ and R₂ can beeither the same or different. More preferred are di-ionyl ethers i.e.ethers derived from α, β or γ-ionol.

The ethers according to the invention are not only novel as aromaprecursors, but these compounds are also novel as such.

It is possible to use only one ether compound according to the aboveformula in an aromatizing composition, but if desired, mixtures of twoor more of said ether compounds may be used in such a composition.

It was found that ether synthesis starting from ionol-type alcoholsusing a Lewis acid as a catalyst is a suitable method for synthesizingethers according to the invention. Such a method has been described forthe synthesis of other ethers by S. Kim et al. in J.Org.Chem. 52,3917-3919 (1987). Kim et al. indicate that dichloro ethane may be usedas a solvent in this reaction, but in the case of synthesizing theethers according to the invention other common solvents, e.g.hydrocarbons such as hexane, gave good results as well. It was foundthat zinc halides, and in particular zinc chloride are suitable Lewisacid catalysts. The desired ethers can be isolated from the reactionmixture in a conventional way. "Aroma" is herein used as a collectiveterm for perfume and flavour. In this connection, "aromatizingcomposition" is used as a collective term for perfume composition andflavouring composition, and similarly "aromatizing" is used as acollective term for flavouring and perfumery.

The compounds according to the invention can be added as such to aproduct to provide a flavour or odour on heating the said product orthey can be incorporated first in a mixture which can be used as aflavour composition or perfume composition for application to such aproduct. In this connection the terms "flavouring composition" and"perfume composition" mean mixtures of flavouring components or perfumecomponents respectively and/or other components, if desired dissolved ina suitable solvent or mixed with a powdered substrate or processed toform a powdered product. Such flavouring or perfume compositions mayalso include other flavouring or perfume precursor systems respectively.The said compositions are used to impart a desired flavour or odour toproducts of all types or to reinforce, to improve or to change theflavour or odour which these products already have or develop, or changethe flavour or odour on usage of these products.

Alternatively, organoleptically useful mixtures, hereinafter referred toas "organoleptic mixtures", will be developed when the ethers accordingto the invention are thermally degraded as such. Said organolepticmixtures may thereafter be used for flavouring or perfuming purposes,either by adding them as such to products to be flavoured or perfumed,or as a part of a flavouring or perfume composition.

Basic perfume and flavour substances which can be advantageouslycombined with the compounds according to the invention or the saidorganoleptic mixtures are, for example, natural products such asextracts, essential oils, absolutes, resinoids, resins, concretes etc.,but also synthetic basic substances such as hydrocarbons, alcohols,aldehydes, ketones, ethers, acids, esters, acetals, ketals, nitriles,etc., including saturated and unsaturated compounds, aliphatic,carbocyclic and heterocyclic compounds.

Such basic substances are mentioned, for example, in S. Arctander,Perfume and Flavor Chemicals (Montclair, N.J., 1969), in S. Arctander,Perfume and Flavor Materials of Natural Origin (Elizabeth, N.J., 1960),in T. E. Furia et al., CRC Fenaroli's Handbook of Flavor Ingredients,2nd edition (Cleveland, CRC Press Inc., 1983), H.B. Heath, Source Bookof Flavours, The Avi Publishing Co. Inc. Westport, Conn. (1981and"Flavor and Fragrance Materials--1991", Allured Publishing Co. Wheaton,Ill. USA.

Examples of perfume components which can be used in combination with thecompounds according to the invention or with said organoleptic mixturesare geraniol, geranyl acetate, linalol, linalyl acetate,tetrahydrolinalol, citronellol, citronellyl acetate, dihydromyrcenol,dihydromyrcenyl acetate, tetrahydromyrcenol, terpineol, terpinylacetate, nopol, nopyl acetate, 2-phenylethanol, 2-phenylethyl acetate,benzyl alcohol, benzyl acetate, benzyl salicylate, styrallyl acetate,benzyl benzoate, amyl salicylate, dimethylbenzyl-carbinol,trichloromethylphenylcarbinyl acetate, p-tert-butyl cyclohexyl acetate,isononyl acetate, vetiveryl acetate, vetiverol, α-hexylcinnamaldehyde,2-methyl-3-(p-tert-butylphenyl)propanal,2-methyl-3-(p-isopropylphenyl)propanal, 3-(p-tert-butylphenyl)propanal,tricyclodecenyl acetate, triclyclodecenyl propionate,4-(4-hydroxy-4-methyl-pentyl)-3-cyclohexenecarbaldehyde,4-(4-methyl-3-pentenyl)-3-cyclohexenecarbaldehyde,4-acetoxy-3-pentyltetrahydropyran, 3-carboxymethyl-2-pentylcyclopentane, 2-n-heptylcyclopentanone, 3-methyl-2-pentyl-2-cyclopentenone,n-decanal, n-dodecanal, 9-decenol-1, phenoxyethyl isobutyrate,phenylacetaldehyde dimethylacetal, phenylacetaldehyde diethylacetal,geranyl nitrile, citronellyl nitrile, cedryl acetate,3-isocamphylcyclohexanol, cedryl methyl ether, isolongifolanone,aubepine nitrile, aubepine, heliotropin, coumarin, eugenol, vanillin,diphenyl oxide, hydroxycitronellal, ionones, methylionones,iomethylionones, irones, cis-3-hexenol and esters thereof, indan muskstetralin musks isochroman musks macrocyclic ketones, macrolactone musksethylene brassylate, aromatic nitromusks.

Auxiliary materials and solvents which can be used in perfumecompositions which contain compounds according to the invention are, forexample: ethanol, isopropanol, diethyleneglycol monoethyl ether, diethylphthalate etc. Such auxiliary materials and solvents for flavourcompositions are, for example: ethanol, diethyleneglycol monoethylether, propylene glycol, glycerol and triacetin.

The quantities of the compounds according to the invention or saidorganoleptic mixtures to be used may be strongly divergent and depend,inter alia, on the product in which the compounds are used and on thenature and the quantity of the other components of a flavouring orperfume composition. In perfume and flavouring compositions an amount of0.01% or more of the compounds according to the invention will generallyhave a clearly perceptible organoleptic effect. The amount of compoundsaccording to the invention present in end products will generally be0.01 ppm or more.

The products to which the ethers according to the invention can beadded, either as such or in a composition or on a suitable carrier, arenumerous. Application to products which are in some stage submitted to aheating, smouldering or burning step is especially suitable, becausethen an odour and/or flavour will be released on usage of said products.Products of this type include, inter alia, candles, ironing aids,matches, aids for lighting a fire, fuel for e.g. lighters, lamps and thelike, products used with or intended for cooking, frying, baking,barbequeing or microwave heating. Other suitable applications may beproducts intended for cleaning purposes where heating is applied duringsome stage of the cleaning process, such as oven cleaners, detergents,fabric washing compositions, fabric softeners, flat-iron cleanersetcetera.

It is also possible to combine degraded and undegraded ethers accordingto the invention for flavouring and/or perfumery purposes.

As outlined above, the ethers according to the invention are easilydegraded by heat, especially in the presence of oxygen or an oxygencontaining gas such as air. Because the ethers according to theinvention are yet relatively thermostable, it is preferred that theethers according to the invention or products containing them are heatedto at least 60° C. Under these conditions, complex mixtures havingdesirable organoleptic properties are developed. For the development ofsaid complex mixtures it is more preferred that the ethers are heated to120° C. or above, even more preferably to 150° C. or above.

The time needed for the development of a sufficiently strong odour orflavour will depend, inter alia, on the specific products whereto theethers according to the invention are applied and the maximumtemperature reached.

The compounds according to the invention and the said organolepticmixtures are especially suitable for flavouring tobacco, tobaccoproducts and tobacco substitutes or other materials used for themanufacturing of tobacco products such as e.g. cigarette wrappers. Theterm "tobacco" will be understood herein to mean natural products suchas, for example, Virginia, Burley, Turkish or Maryland tobacco,flue-cured tobacco and others including tobacco-like or tobacco-basedproducts such as reconstituted or homogenized leaf and the like. In thisconnection "tobacco products" mean tobacco or tobacco substitutecontaining products designed, intended or used for smoking, such ascigarettes, cigars, pipe tobacco etcetera. The term "tobaccosubstitutes" is to be understood herein to be compounds, compositions,materials or structures intended to replace natural tobacco or tobaccoproducts partly or completely. The flavour is released to the smokeimmediately or shortly after the tobacco products or tobacco substitutesare used as intended, i.e. smoked.

A number of ways are possible for applying the compounds according tothe invention (either as such or as a part of a composition) to tobaccoproducts or tobacco substitutes, strongly depending on the specificnature of the product or substitute.

In the case of tobacco, methods for applying flavours or flavouringcompositions are known in the art and include simply spraying oratomizing the flavour or flavouring composition (sometimes diluted witha suitable solvent like alcohol) over the bulk of the tobacco. Anothermethod may be finely dispersing an emulsion over the bulk of thetobacco, wherein the emulsion comprises an emulsifier, an aqueous phase,and an oil phase, which may comprise compound I, II, III or acombination thereof. Other compounds may be included in the formulation.Such a method is described in more detail in EP-A-366 835. Still anothermethod for applying the flavour compounds to the tobacco is a method inwhich the flavour components (optionally mixed with other components)are micro-encapsulated and subsequently mixed with the tobacco bulk.Optionally an adhesive may be used to fix the micro-capsules to thetobacco leafs. Thus, tobacco, tobacco products or tobacco substitutesflavoured with the compounds according to the invention, either as suchor as a part of a composition, can be obtained.

The invention is illustrated by the following examples but is in no waylimited thereto.

EXAMPLE 1 Preparation of Di-β-Ionyl Ether

Zinc dichloride (1.4 kg) was added to hexane (45 kg) together withβ-ionol (11 kg), all components being substantially dry, and the mixturewas stirred at 20° C. for 2.5 hours. Hereafter the mixture wasthoroughly washed (by stirring for 15 minutes and subsequent phaseseparation) with a mixture of 4.5 kg methanol and 0.5 kg water (twice),and 5 kg water. The solution was then dried with sodium sulphate,whereafter the hexane was boiled off under reduced pressure at 30° C.,during which 40kg of hexane was recovered. 10.0 kg of β-dionyl ether wasobtained.

EXAMPLE 2

A flavouring composition having a Virginia tobacco flavour was preparedby mixing the following compounds in the amounts indicated (in parts byweight on a total of 1000):

    ______________________________________                                        Benzyl alcohol       263                                                      γ-Butyrolactone                                                                              250                                                      Ethyl palmitate      200                                                      Acetic acid          60                                                       γ-Valerolactone                                                                              60                                                       Farnesol             25                                                       Valeric acid         20                                                       γ-Heptalactone 20                                                       Ethyl laurate        20                                                       Ethyl decanoate      10                                                       Malt extract (20% dry matter)                                                                      10                                                       Coffee extract       10                                                       Furfural             10                                                       Guajacol             5                                                        Benzaldehyde         4                                                        Acetophenone         4                                                        Methylheptenone      4                                                        Di-β-ionyl ether                                                                              25                                                       ______________________________________                                    

EXAMPLE 3

A composition suitable for flavouring the side stream smoke of tobacco,tobacco products or tobacco substitutes was prepared by mixing thefollowing compounds in the amounts indicated (in parts by weight on atotal of 1000):

    ______________________________________                                        Apricot oleoresin                                                                              350                                                          Olibanum resin   30                                                           Vanilline        25                                                           Sandalwood oil   5                                                            Ylang Ylang oil  2                                                            Coriander oil    2                                                            Di-β-ionyl ether                                                                          10                                                           Propylene glycol 576                                                          ______________________________________                                    

We claim:
 1. An ether having the formula R₁ --O--R₂ wherein R₁ and R₂are radicals according to the following formula: ##STR2## and wherein: Rdenotes either hydrogen or a lower alkyl group, and double bonds can bepresent at the positions indicated by the dotted lines.
 2. An etheraccording to claim 1, wherein R is hydrogen.
 3. An ether according toclaim 1, wherein R is methyl.
 4. An ether according to any one of claims1-3, wherein R₁ and R₂ are the same.
 5. An ether according to any one ofclaims 1-3, wherein R₁ and R₂ are different.
 6. An ether according toclaim 1, wherein R₁ and R₂ are ionyl radicals.
 7. An ether according toclaim 1, wherein the ether decomposes to at least one volatilearomatizing compound when heated.
 8. A composition intended to be atleast partially heated, smouldered or burned, comprising at least oneether according to claim 1.